1. Field of the Invention
The present invention relates to an oscillator circuit and a semiconductor device having the oscillator circuit.
2. Description of Related Art
Electronic circuits built in conventional various electronic apparatuses often use a reference clock signal oscillating at a constant frequency, and an oscillator circuit is used as a circuit for generating the reference clock signal.
A conventional circuit often used as this oscillator circuit has a structure such as shown in FIG. 9. Namely, an oscillator circuit 101 shown in FIG. 9 has: two comparators CMP101 and CMP102 for comparing an input signal S101 with reference signals S102 and S103 having different voltages; an RS type flip-flop FF101 operating by receiving output signals S104 and S105 of the comparators CMP101 and CMP102; a switching transistor TR101 intermittently operating in response to an output signal S106 from the RS type flip-flop FF101, and a capacitor C101 for generating the input signal S101 through charge/discharge cooperating with the intermittent operation of the switching transistor TR101.
In this oscillator circuit 101, the two comparators CMP101 and CMP102 operate alternately to make the voltage of the input signal S101 generated by the capacitor C101 have a value between the reference signals S102 and S102 having different voltages, and in response to this operation, the RS type flip-flop FF101 outputs the output signal S106 having a predetermined frequency determined by a charge time and a discharge time of the capacitor C101.
Refer to Japanese Patent Application Publication No. 2004-15447.